1. Field of the Invention
The present invention relates to an optical termination unit integrally constructed with a connection panel to be secured to a building or the like for allowing connection of an optical fiber thereto. The optical termination unit of the present invention is useful as a small, compact camera terminal connecting board when a television broadcasting system or the like is constructed.
2. Description of the Related Art
As an optical termination unit integrally constructed with a connection panel to be secured to a building or the like for connecting an optical fiber, the prior art described in Japanese Unexamined Patent Application Publication No. 2004-170926, for example, is publicly known. FIG. 15 of this patent application is a side view of the apparatus described in Japanese Unexamined Patent Application Publication No. 2004-170926 (FIG. 4). A connection unit 4 in the figure, for securing the armor (outermost resin layer) of an optical cable 6 and the end of a tension member 8 of the optical cable 6 by means of fixtures 23, 24, is secured to a second surface 3b slanting upward and extending inward toward an outer frame panel 2. The connection unit 4 allows the optical cable 6, more resistant to bending, pulling or the like than an optical fiber, to extend rearward, reducing the possibility of being mistakenly cut off optical fiber during cable laying or servicing operations.
The apparatuses in the prior art described in Japanese Application for Design Registration No. 1184727 and Japanese Application for Design Registration No. 1185087 are believed to be similar in structure to the above-mentioned apparatus.
However, since the connection unit 4 is secured to the second surface 3b, the extending direction of the optical cable 6 is necessarily limited to the second surface 3b or its close vicinity. Accordingly, if the optical cable 6 is introduced into the optical termination unit in a direction other than the extending direction, the optical cable 6 must be bent so as to enter the unit.
Meanwhile, from the viewpoint of loads put on the optical cable and its fixtures as well as their durability and reliability, it is generally undesirable to bend the optical cable 6 with a curvature radius of 6 to 7 cm or less since the optical cable 6 is designed to provide sufficient resistance to bending or pulling, as shown above.
Continuous bending of the optical cable with a much smaller curvature radius than mentioned above is not always easy during work on the optical cable. Accordingly, the structure of the optical termination unit which forces such bending places limitations on working efficiency associated with optical cable laying or servicing operations.
For this reason, in the above prior art, vertically introducing the optical cable 6 into the optical termination unit from directly above or below or horizontally introducing the optical cable 6 into the optical termination unit from behind tends to pose a problem regarding routing of the optical cable 6 within the internal space of the optical termination unit. In these cases, namely, if the optical cable 6 is introduced, in particular, vertically or horizontally from behind, larger lower limits of curvature radius of the optical cable 6 within the range allowing the cable to be easily bent during work will result in an increase in the size of the optical termination unit, diminishing the compactness of the optical termination unit. Besides, from the viewpoint of standardization of product specifications, it is undesirable to alter the enclosure size or shape of the optical termination unit, depending on the incoming direction of the optical cable.
Furthermore, when an optical cable installed inside a building is taken to the outside through a pillar or wall, the extending direction of the cable is usually vertical or horizontal, considering ease of design or ease of construction of a building. It is likely that the direction of a cable coming into the optical termination unit is necessarily limited to these directions. For this, addressing the above problem is important and unavoidable, from the viewpoint of industries including the construction industry. In other words, from the viewpoint of ease of design or ease of construction of a building, it is undesirable that the optical termination unit have a structure where the second surface 3b is inclined at approximately half of a right angle.
With the increasing number of optical fibers or wires contained in optical cables and higher rigidity of optical cable tension members or armor, there has been a resultant increase in the lower limit of curvature radius permitted for an optical cable, making the above problem more serious in the future.